Biology of the gametocyte

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The gametocyte pathway

The gametocyte is the committed sexual form of the malarial parasite. Gametocytes have either male or female form (a higher percentage are female). However this form should probably be considered as “dormant” in blood, since they do not develop further until ingested by a mosquito - following a temperature drop in the mosquito foregut the gametocytes then rapidly form the active sexual form – either a single female gamete or 8 male gametes (see section on re-infection of the mosquito).

Generally male gametocytes (microgametocytes) are smaller then the female form (macrogametocytes). This is shown in the image below:

Frequency large vs small 1. P.malariae just a question of scale 2. P.falciparum neatly shown by red cell

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Morphological features and relevance

(1) P.falciparum – typically elongated or “banana” shaped forms
(2) P.malariae – typically small and neat rounded forms
(3) P.vivax – typically very large and often irregular
(4) P.ovale – typically sightly enlarged and may be fimbriated

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  Typical curved gametocyte of P.falciparum

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  Small "neat" and round gametocytes in P.malariae

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  Very enarged irregular P.vivax gametocytes

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  Enlarged forms in P.ovale with fimbriation

→ Click for the clinical gametocyte gallery

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Relevance of gametocytes to clinical biology

Following treatment of malaria these forms may persist (depending on the nature of the treatment) particularly in the first week but sometimes up to 28 days (unlike the asexual forms that generally disappear more rapidly).

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